What we feed the animals we eat

Andy Badeker, Tribune staff reporterCHICAGO TRIBUNE

The worries over anthrax and its antibiotic of choice, Cipro, raise a couple of other unsettling questions: What happens when disease-causing microbes learn to shrug off the drugs designed to kill them? And what happens when those microbes start showing up on your food?

Salmonella does not have the panic factor of anthrax, even though the food-borne bacterium has killed a lot more people. But a study published Oct. 18 in The New England Journal of Medicine found antibiotic-resistant salmonella on ground chicken, turkey, pork and beef bought at Washington, D.C., supermarkets.

That's not news. Resistant bacteria have been on the public-health radar screen for years, and the proportion of tainted samples (20 percent overall) was about the same as in previous studies. What was alarming was the increased number and virulence of the salmonella types in this study, said Dr. Sherwood L. Gorbach, who wrote the accompanying editorial calling for an end to the routine feeding of antibiotics to the country's food animals.

"They found a particularly nasty strain called DT104," which has been associated with increasing numbers of food poisoning outbreaks, Gorbach said. "It's virulent and resistant." Of the salmonella types isolated in the study, 84 percent were resistant to at least one antibiotic. Fifty-three percent were resistant to at least three antibiotics.

Making them fatter, faster

Low doses of antibiotics have been added to animal feed since the 1950s boom in drug development, when producers realized that such "subtherapeutic" use resulted in efficient meatmaking.

"The animal gains weight faster with less feed," said Dr. Linda Tollefson, deputy director of the Center for Veterinary Medicine at the U.S. Food and Drug Administration. The animals aren't sick, hence the term "subtherapeutic."

Unfortunately, that's also a recipe for resistance, Tollefson acknowledges. Billions of animals fed tiny doses of antibiotics produce resistant bacteria that pass on their survival skills. These bacteria infest the feedlot or poultry house and wait for the next herd or flock to arrive.

"My view is that [antibiotics] should be used for preventing infection or treating infection, not for promoting growth in animals," said Dr. Stuart Levy of the Alliance for the Prudent Use of Antibiotics, a Boston group. "Antibiotics are precious drugs, useful to people as well as animals."

Nobody is arguing that sick animals shouldn't be treated. But the suggestion of a ban on subtherapeutic antibiotics produces plenty of disagreement.

Chicken on the front lines

Because the New England Journal of Medicine study found resistant bacteria on 35 percent of its chicken samples (compared with 24 percent for turkey, 16 percent for pork and 6 percent for beef), the industry is feeling defensive. Representatives hold up year 2000 figures from the Department of Agriculture showing salmonella rates of 13.8 percent for ground chicken and 9.1 percent for whole broilers. The New England study took its samples in 1998.

"Chicken is being blamed for a problem that is broader," said Richard Lobb, a spokesman for the National Chicken Council in Washington, D.C. He stresses that physicians' over-eager prescribing habits contribute to resistance. "In Washington, having your packet of Cipro is a status symbol these days," he said.

Gorbach said as much in his editorial: Indiscriminate prescribing has bred increasing resistance into the bacteria that cause pneumonia, staph and gonorrhea.

"I'd have to say that pneumonia kills more people than food poisoning," Gorbach said. "On the other hand, more of the population is threatened by food poisoning."

And the bulk of antibiotics is consumed by food animals, not humans, which makes sense once you realize that the U.S. is home to a lot more cattle, hogs and chickens than people.

The chicken industry also disputes the contention that subtherapeutic antibiotics permit cheap feed and crowded, dirty conditions for birds.

"Antibiotics are not used as a substitute for square footage," said Bill Roenigk, the Chicken Council's vice president, and "they are not going to be a substitute for good animal husbandry practices."

Without antibiotics, Roenigk said, producers would have to accept lower production and higher disease rates. "They then have to medicate."

A different way

Yes and no, said Susan Ranck, quality assurance manager at Bell & Evans, a producer in Fredericksburg, Pa., that boasts of its antibiotic-free birds.

"We do not see the rate of gain" that an antibiotic-dependent producer has, she said, but her firm doesn't have more sick birds. "We've proven that with proper management, you don't have to use antibiotics at any level." Any flocks that do require medication aren't sold as Bell & Evans.

Proper management in Bell & Evans case extends to requiring producers to disinfect chicken houses between flocks. Lobb of the Chicken Council wrote in an e-mail that "some companies require the producer to clean out between flocks. Others require the producer to rake out the 'caked' portions and top-dress with new litter as needed. In many cases a total clean-out will occur once a year." Raising a chicken from chick to slaughter weight takes about 45 days, Roenigk said.

Consumers do pay something for the difference: At Treasure Island, whole Bell & Evans chickens cost $1.69 a pound compared to regular chickens at $1.49 a pound. A whole chicken from Miller's, also antibiotic-free, was $1.79 a pound at Whole Foods Market.

Gorbach said that in Europe, a ban on subtherapeutic feeding has led to a "zero-sum game," in which consumers don't pay more and producers don't lose money.

All in the family

And though producers of meat animals have said that the drugs they use subtherapeutically are not used in humans, that's not exactly true. Popular choices are penicillin, tetracycline, erythromycin and virginiamycin, said the FDA's Tollefson.

"All of these, or an analog of these, are used in humans, except for virginiamycin," Tollefson said. A related drug called Synercid is a human drug, though, and resistance to virginiamycin confers resistance to Synercid.

Such cross-resistance is common. "If you're in the same family of drugs, then resistance to any member of that family is going to be elicited by any other member of that family," said Levy of the Alliance for the Prudent Use of Antibiotics.

It is this phenomenon that led the FDA to withdraw its approval of a fluoroquinolone to treat sick poultry. (It is not used subtherapeutically.) That family of drugs combats campylobacter, the most common bacterial cause of diarrhea in the U.S. and the most common contaminant of chicken. The poultry version is enrofloxacin; the human version is ciprofloxacin, also known as Cipro.

"We are in the process of removing it from the market," Tollefson said. Her agency also is looking at subtherapeutic uses of virginiamycin, as well as penicillin, tetracycline and erythromycin. "Our case has to be pretty strong," showing a clear link between sick people and antibiotics in animal feed. "An outright ban of all the drugs is not legally possible for the FDA to do."

As for the studies in The New England Journal of Medicine, Lobb of the Chicken Council is dismissive: "These reports do not indicate why we should make any substantial changes."

Staying well

From the point of view of a consumer standing in front of a meat case, solving the problem of resistant bacteria may seem impossible. But the short-term solution is a familiar one: Cook that ground beef, and pork, and chicken.

These bacteria, in whatever numbers and of whatever virulence, are on raw products. "You don't eat raw chicken," Lobb said.

Gorbach concurs that "simple rules of hygiene in the kitchen" can prevent cross-contamination--don't use that boning knife to chop an onion without a good dose of soap and water in between. But he goes further.

"Consumers are also citizens," he said, and can contact their elected representatives if they feel like it. "These are issues that are under the purview of the federal government. Congress is taking an interest."

In the meantime, take comfort in the knowledge that "these are simple bacteria," he said, easily killed by thorough cooking. "They don't form spores, either."